The present invention relates to a picture information reading apparatus for reading picture information by successive scanning using a plurality of linear image sensors.
In a picture image reading apparatus for reading picture information by successive scanning (raster scanning), generally, a plurality of linear image sensors (hereinafter merely referred to as image sensors) such as charge coupled devices (CCDs) are disposed in the main scanning direction of an original document, and picture signals produced by these image sensors are connected to form a single line of a serial picture signal.
FIG. 1 shows the arrangement of an optical system of such apparatus. In this apparatus, three image sensors 1.sub.1, 1.sub.2 and 1.sub.3 are employed and three lenses 2.sub.1, 2.sub.2 and 2.sub.3 are provided respectively corresponding to the image sensors. The picture information on an original document 3 is divided into three parts in the main scanning direction and the three image sensors 1.sub.1 -1.sub.3 read these three parts, respectively, correspondingly through the lenses 2.sub.1 -2.sub.3. In such a conventional reading apparatus, the following has been required of the optical system:
(1) The respective focuses of the lenses 2.sub.1 -2.sub.3 should be correctly matched to the corresponding image sensors 1.sub.1 -1.sub.3 ;
(2) The respective image sensors 1.sub.1 -1.sub.3 should be disposed at a predetermined interval in the main scanning direction so that one line of picture information can be equally divided into three parts; and
(3) The respective image sensors 1.sub.1 -1.sub.3 should be arranged in a straight line in the main scanning direction.
Requirement (3) requires the satisfaction of the following two particular conditions:
(i) The respective image sensors 1.sub.1 -1.sub.3 should be disposed in the main scanning direction; and
(ii) The respective image sensors 1.sub.1 -1.sub.3 should be aligned in a straight line.
Accordingly, the adjustment of the optical system has heretofore required a skilled operator and substantial time.